Backlight-type liquid-crystal displays, liquid-crystal TVs, illumination signboards and others with a built-in light source therein have been much popularized. Of such built-in light sources, a typical structure of an underlight-type backlight comprises, as in FIG. 2, a housing 11 that serves both as a profile case and as a light reflector, a diffuser 14, and a light source such as a cold-cathode lamp 15. A typical structure of a sidelight-type backlight comprises, as in FIG. 3, a light waveguide with a dot print 12 on a transparent acrylic plate 13, a light reflector 11, a diffuser 14, and a light source such as a cold-cathode lamp 15. In these, the light from the light source is reflected on the light reflector, and forms uniform planar light through the diffuser. With the recent tendency toward large-size displays, some improvements have been made in built-in light sources by increasing their output power and by increasing the number of the light source lamps therein. For increasing the brightness of these devices, plural light sources may be disposed, as in FIG. 2 and FIG. 3.
Heretofore for the light reflectors for such applications, the housing for the profile case is often painted white or a white polyester film (e.g., Patent Reference 1) is much used. However, the white painting could not satisfactorily increase the brightness by reflected light, and a light reflector that comprises a white polyester film is often problematic in point of its discoloration (yellowing) owing to the recent increase in the quantity of light, and materials that could secure high brightness are less discolored have become desired. Accordingly, recently, a high-brightness light reflector comprising a white polyolefin film that is discolored little has been proposed (e.g., Patent References 2 to 5).
However, when a conventional white polyester film or white polyolefin film is used in an underlight-type light source unit with plural light sources set therein for increasing the brightness thereof, it brings about a problem in that there appear emission lines and the brightness thereby becomes uneven. Specifically, in the case where plural light source lamps are installed, then the reflected light may gather owing to the light-reflecting property of the housing structure or the light reflector (white film), and, for example, as in FIG. 2, the brightness just above (adjacent to) the light source lamp may increase. Accordingly, a light reflector capable of preventing the brightness unevenness or the emission line generation to be caused by the localization of the reflected light is desired. The emission line that is discussed here does not mean the phenomenon that the area around the light source lamp has a partly increased brightness owing to the light leakage from the light source therearound.    Patent Reference 1: JP-A 4-239540    Patent Reference 2: JP-A 6-298957    Patent Reference 3: JP-A 2002-31704    Patent Reference 4: JP-A 8-262208    Patent Reference 5: WO03/014778